Exemplary embodiments of inventive concepts relate to microlens array films and display devices including the same.
With the advance in display technology applied to various types of terminals such as mobile phones, navigation systems, digital information displays (DIDs), and tablet PCs, projectors, and television sets that are now currently on the market, not only high-resolution screen but also three-dimensional (3D) images or virtual images may be provided. Virtual screen technology employs a projection method based on laser a light source, a micromirror array, and a microlens array. Currently, a user may recognize a position when the user comes close to or touches a specific portion of a virtual screen through linkage of an infrared sensor. Accordingly, the technology has been applied to develop virtual keyboards capable of overcoming touch error or inconvenience of writing documents or texts which may result from miniaturization of computers or mobile terminals. In addition, 3D images have been mainly obtained by a stereoscopic method which provides 3D effect by implementing perspective resulting from visual disparity of images perceived by two eyes. However, since the stereoscopic method obtains stereoscopic images with depth of the front, there is a technical limitation that the 3D effect is clearly distinguished according to an image viewing angle. In addition, viewers suffer from disadvantages such as eye fatigue and dizziness when they watch a 3D screen. Meanwhile, a holographic technology allows omnidirectional 3D effect to be implemented to the level equivalent to an actual image of object. For this reason, the holographic technology has been attracting attention to implement a 3D display without wearing auxiliary equipment.
In order to implement a virtual screen or 3D images similar to actual images on various types of electronic devices, it is necessary to use a microlens array that is designed to meet their needs. Currently, passive lens layers standardized depending on purposes have been used. Currently, a microlens structure has been manufactured by variously methods such as a laser induced dry etching method, a method using a reflow phenomenon of a polymeric substance, a photolithography method using a diffuser, a laser chemical deposition method, and a focused ion beam (FIB) milling method. The method using a reflow phenomenon has been mainly used due to advantage in manufacturing lenses of various sizes, easy control, low production costs, and simple process. This method includes forming a cylindrical photoresist pattern on a substrate and applying heat to a resultant structure to manufacture a spherical lens based on surface tension. However, the spherical lens is vulnerable to heat and shock, i.e., poor in durability, flexibility of the spherical lens is not ensured, and the spherical lens is strongly affected by an external environment. In order to overcome these disadvantages, a method of transcribing a lens-shaped structure to a substrate by reactive ion etching (RIE) and an imprinting method using a PDMS mold and UV cured polymer have been used. Unfortunately, the former requires additional polishing because of a problem in surface roughness after using RIE, and both the former and the latter may be applied only to manufacturing of passive lenses and still have difficulty in manufacturing a microlens array with ensured flexibility in terms of characteristics of a structure material.